Distillate fuel compositions for improved combustion and engine cleanliness

ABSTRACT

The invention provides a distillate fuel additive composition, and also a fuel composition containing a distillate fuel, an overbased calcium sulfonate detergent, a succinimide dispersant, and an organomanganese compound. Also provided is a method for improving the cleanliness of diesel fuel intake systems by the combustion in said systems of a distillate fuel containing the fuel additive composition.

FIELD

The present invention relates to a synergistic interaction between anoverbased calcium sulfonate detergent and an ashless succinimidedispersant that allows for the formulation of improved distillate fueladditive packages. In addition to the metallic detergent and the ashlessdispersant, the additive compositions contain an organometallic complexof manganese. Distillate fuels treated with the additive compositionsexhibit improved combustion because of the detergent and theorganometallic manganese compound and good fuel system cleanlinessbecause of the detergent/dispersant interaction.

BACKGROUND

A great deal of prior art has been devoted to formulating distillatefuel additive compositions to provide environmental benefits when thefuel is combusted. Such benefits include, for example, reduced emissionsof noxious pollutants such as oxides of nitrogen and particulate matter,reduced acidity of emitted particulates, and better fuel economy (whichamounts to lower emissions of carbon dioxide per amount of fuel burned).The effects of these fuels on the cleanliness of fuel systems, e.g., onthe buildup of carbon and lacquer on the fuel injectors found in dieselengines, has received less study.

A need exists for a distillate fuel additive composition that providesfor the simultaneous achievement of improved combustion, fuel andcombustion system cleanliness, improved fuel economy, and reduction inpollutant generation.

SUMMARY OF THE EMBODIMENTS

An embodiment presented herein provides a fuel additive compositioncomprising an organometallic manganese compound, an alkyl-substitutedsuccinimide ashless dispersant, and an overbased calcium sulfonatedetergent of TBN above about 200. In another embodiment the TBN of theoverbased calcium sulfonate is about 300.

Another embodiment provides a fuel comprising a major amount of a middledistillate fuel and a minor amount of a fuel additive compositioncomprising an organometallic manganese compound, an alkyl-substitutedsuccinimide ashless dispersant, and an overbased calcium sulfonatedetergent of TBN above about 200.

Accordingly, in one example herein is provided a method of for improvingthe cleanliness of a fuel intake systems by use in the fuel intakesystem of a fuel containing a fuel additive composition comprising anorganometallic manganese compound, an alkyl-substituted succinimideashless dispersant, and an overbased calcium sulfonate detergent of TBNabout 300.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide further explanation of the presentinvention, as claimed.

DETAILED DESCRIPTION OF EMBODIMENTS

In one embodiment is provided herein distillate fuel additivecompositions for use in distillate fuels that provide enhanced fuelcombustion and, at the same time, superior cleanliness of fuel intakesystems. Distillate fuels are defined herein as petroleum-basedhydrocarbon fuels boiling in the range of about 140-360° C. [284-680°F.] and encompass diesel and biodiesel fuels, jet fuels, marine fuelsand home heating oils. Distillate fuels containing the additivecompositions of the invention show enhanced combustion characteristics.

If certain components of the additive packages described herein arepresent in specific proportions, fuels containing the additive packagesalso show excellent fuel injector cleanliness as measured by the CumminsL10 diesel detergency test. This injector cleanliness is exhibited as aninjector rating of at most 10.0 in the Cummins L10 diesel detergencytest.

Other embodiments herein provide an additive composition, a distillatefuel containing the additive composition, and a method of improving thecleanliness of fuel intake systems by use of the fuel containing theadditive composition.

In an embodiment, the additive composition contains at least anorganometallic complex of manganese, an overbased calcium sulfonatedetergent and an ashless succinimide dispersant such that when theadditive composition is dissolved in a distillate fuel, the followingrelationship is satisfied:−0.159x+0.243y−0.0143xy≦−8.4where

-   -   x=concentration of succinimide (in pounds per thousand barrels)    -   y=concentration of overbased calcium sulfonate (in PTB)    -   with the following limitations:    -   x=20-35, preferably 25-30, and y=10-120, preferably 30-50.

The organometallic manganese compound does not affect injectorcleanliness. In an embodiment, the organometallic manganese compound maybe present in the fuel at concentrations of up to about 20 PTB.

It has been discovered that the combustion-improving conventionaladditive packages previously known do not necessarily pass the CumminsL10 diesel detergency test (where a pass is defined as an averageinjector rating of 10.0 or less). To identify the components in theadditive composition that affect injector ratings, an experimentaldesign was carried out. A synergy (i.e. a nonlinear interaction) wasobserved between the overbased calcium sulfonate detergent and thesuccinimide dispersant. This was a surprising result which is notanticipated by any prior art.

The results of the experimental design were used to generate a model foraverage injector rating, as follows:Rating=−0.159x+0.243y−0.0143xy+18.4   (1)where

-   -   x=concentration of succinimide (in pounds per thousand barrels,        or PTB)    -   y=concentration of overbased calcium sulfonate (in PTB)        Since the average injector rating must be 10.0 or lower for a        pass in the Cummins L10 test, the equation becomes:        10.0≧−0.159x+0.243y−0.0143xy+18.4   (2)        or        −0.159x+0.243y−0.0143xy≦≦8.4   (3)        The detergent/dispersant synergy is represented by the xy term.

The model was validated by the testing of three new formulations thatsatisfy the above equation:

-   -   1. x=28 PTB, y=32 PTB    -   2. x=26 PTB, y=40 PTB    -   3. x=25 PTB, y=48 PTB

All three formulations gave an average injector rating of below 10.0, inaccordance with the model. Of course, there are an infinite number ofsolutions for x and y in equation 3. Examples of currently practicalsolutions are the following ranges:

-   -   x=20-35, preferably 25-30    -   y=10-120, preferably 30-50

The amount of organometallic manganese compound was shown to have nosignificant adverse effect on injector ratings and is therefore notconstrained by the model represented by equation 3. As an economicmatter only, the amount of manganese compound is, in an embodiment,limited to 20 PTB or less. The benefits derived from the inclusion of amanganese compound are not directly related to injector ratings, but aremuch more prevalent in the areas of particulate emission reduction,reduced NO_(x) and SO_(x), reduced hydrocarbons, improved fuel economy,and combustion improvement.

Especially useful herein is methylcyclopentadienylmanganese tricarbonyl(MMT®) as the organometallic manganese compound, a succinimide preparedfrom 850 to 2100-MW PIBSA and a polyalkylene polyamine approximatingtetraethylenepentamine in composition as the ashless dispersant, and anoverbased calcium sulfonate of TBN up to about 300 as the detergent.MMT® is available from Ethyl Corporation, Richmond, Va. The diesel fuelused in the Cummins L10 study was a high-sulfur (0.4wgt % sulfur) fuel,but any diesel fuel (including low-sulfur and ultralow-sulfur fuels) maybe used. A separate L10 experiment has shown that the addition of2-ethylhexyl nitrate cetane improver to a fuel containing the inventiveadditive does not degrade the detergent performance.

The following examples further illustrate aspects of the presentinvention but do not limit the present invention.

EXAMPLES

Since the Cummins L10 test was designed to evaluate additives and fuelsfor on-road use in North America, HiTEC®-4080 Fuel Additive was used inthis example. This additive is Ethyl Corporation's antifoam-freeGreenburn® road diesel fuel additive package, used with a recommendedtreat rate of 500 ppm (w/w). The formulation is shown in Table 1. TABLE1 Composition of HiTEC ® 4080 ppm component PTB component Component %weight at 500 ppm total at 500 ppm total HiTEC ® 9645 15.34 76.7 22.82-ethylhexanol 46.22 231.1 68.8 HiTEC ® 611 32.16 160.8 47.9 HiTEC ® 5360.93 4.7 1.4 D-5021 0.97 4.9 1.5 HiTEC ® 3062 4.38 21.9 6.6

For the purposes of this example, the European components D-5021(demulsifier) and HiTEC® 536 (corrosion inhibitor) were replaced withthe North American components Tolad 9310 and 50% dodecenylsuccinic acid,respectively, on an equivalent weight basis. These components were heldconstant at the above concentrations in every test. The componentsexpected to have significant effects on Cummins L10 ratings were HiTEC®9645 (a succinimide-based dispersant), HiTEC® 611 (overbased calciumsulfonate) and HiTEC® 3062 (62% MMT® in aromatic solvent).

The resulting two-level, three-factor (2³) design is shown in FIG. 1;the numbers along the axes denote concentrations in PTB.

All tests were carried out in the same Cummins L10 engine and in thesame batch of high-sulfur Cat 1K fuel. The test order was randomized.The results are shown in Table 2. TABLE 2 Cummins L10 results for H-4080experimental design PTB H- PTB H- Avg. flow Avg. CRC Test no. PTB H-9645611 3062 loss (%) rating D102-97-1 0 0 6.6 3.2 19.1 D102-98-1 23 0 0 4.214.7 D102-99-1 23 0 6.6 2.9 15.3 D102-100-1 23 48 0 2.3 9.9 D102-101-1 048 6.6 8.9 34.7 D102-102-1 11.5 24 3.3 4.1 16.8 D102-103-1 0 48 0 4.025.9 D102-104-1 23 48 6.6 3.1 11.9 D102-105-1 0 0 0 1.9 18.2

An analysis of variance (ANOVA) on the data in Table 2 showed thataverage flow loss was independent of all three factors. The ANOVA forCRC rating is shown below. Analysis of Variance for CRC Source Sum ofSquares Df Mean Square F-Ratio P-Value A (H-9645) 265.651 1 265.65129.81 0.0028 B (H-611) 28.5012 1 28.5012 3.20 0.1337 AB 124.031 1124.031 13.92 0.0136 Total error 44.5563 5 8.91125 Total (corr.) 462.748

-   -   R-squared=90.3712 percent    -   R-squared (adjusted for d.f.)=84.5939 percent    -   Standard Error of Est.=2.98517    -   Mean absolute error=1.55556    -   Durbin-Watson statistic=2.10796

HiTEC® 3062 and the higher-order terms AC, BC and ABC were significantat less than the 85% confidence level and are therefore excluded. Themodel coefficients are as follows:

Regression coeffs. for CRC constant = 18.4375 A (H-9645) = −0.158696 B(H-611) = 0.242708 AB = −0.0142663

The regression coefficients show that HiTEC® 9645 unexpectedly decreasesthe CRC response (a beneficial effect, since lower CRC ratings indicateless injector depositing), while HiTEC® 611 increases the ratings. Thereis a significant negative interaction between HiTEC® 9645 and HiTEC®611, meaning that the deleterious effect of HiTEC® 611 on CRC rating atlow concentrations of dispersant is more than cancelled out at highdispersant concentrations. In other words, HiTEC® 611 improves CRCratings when in the presence of high amounts of HiTEC® 9645. This effectis shown graphically by the interaction diagram in FIG. 2. Ordinarily, ap-value of 0.13 would result in HiTEC® 611 alone being excluded from themodel: this value indicates that the coefficient is different from zeroonly at the 87% confidence level. However, if the model contains aninteraction between HiTEC® 9645 and HiTEC® 611, the HiTEC® 611 termshould also be included to preserve model hierarchy.

Formulations of Modified Dispersant Packages to Pass the Cummins L10Test

From the model developed above, it is therefore possible to adjust thecomponents in, for example, HiTEC®D 4080 in order to hit a desired CRCtarget. As mentioned previously, the maximum CRC rating for a CumminsL10 pass is 10.0. Constant response curves for CRC as a function ofHiTEC® 9645 and HiTEC® 611 concentrations (in PTB) are shown in FIG. 3.

Based on the above model for CRC, any combination of HiTEC® 9645 andHiTEC 611 to the right of the 10.0 contour (the dashed line) in FIG. 3should give a passing Cummins L10 rating. Three points were selected onthe 9.0 contour (the solid line) in the L10 test. The additivecombinations corresponding to these points were:

-   -   1. 28 PTB HiTEC® 9645+32 PTB HiTEC® 611    -   2. 26 PTB HiTEC® 9645+40 PTB HiTEC® 611    -   3. 25 PTB HiTEC® 9645+48 PTB HiTEC® 611

All three packages also contained 6.6 PTB of Ethyl's MMT® as HiTEC® 3062plus solvent, demulsifier and corrosion inhibitor as described above.The resulting Cummins L10 data are shown in Table 3. TABLE 3 Cummins L10results for modified versions of HiTEC ® 4080 Modified package Test no.Avg. flow loss (%) Avg. CRC rating 1 D102-107-2 2.0 8.6 2 D102-107-1 3.18.5 3 D102-109-1 3.3 9.9As expected from the above model and calculations, all three packagespass the Cummins L10 test.

A simple 2³ experimental design has determined the quantitative effectsof various components in a Greenburn® Diesel Fuel Additive package onCummins L10 performance. It was found that the succinimide dispersant(HiTEC® 9645) had a beneficial effect on injector ratings, while theoverbased calcium sulfonate detergent (HiTEC® 611) harmed those ratings.In addition, a strong interaction between these two components wasobserved which reduced the undesirable effect of the detergent. MMT® (asHiTEC® 3062) had no significant effect on injector cleanliness. Themodel derived from the experimental design was used to formulatemodified Greenburn®-type packages that passed the Cummins L10 test.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. As used throughout the specificationand claims, “a” and/or “an” may refer to one or more than one. Unlessotherwise indicated, all numbers expressing quantities of ingredients,properties such as molecular weight, percent, ratio, reactionconditions, and so forth used in the specification and claims are to beunderstood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the specification and claims are approximations that mayvary depending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques. Notwithstanding that the numerical ranges and parameterssetting forth the broad scope of the invention are approximations, thenumerical values set forth in the specific examples are reported asprecisely as possible. Any numerical value, however, inherently containscertain errors necessarily resulting from the standard deviation foundin their respective testing measurements. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the invention being indicated by the followingclaims.

1. A distillate fuel additive composition comprising an organometallicmanganese compound, an alkyl-substituted succinimide ashless dispersant,and an overbased calcium sulfonate detergent.
 2. The fuel additive ofclaim 1 wherein the organometallic manganese compound comprisesmethylcyclopentadienylmanganese tricarbonyl.
 3. The fuel additive ofclaim 1 wherein the succinimide is prepared from polyisobutylenesuccinic anhydride and a polyalkylene polyamine.
 4. The fuel additive ofclaim 1 wherein the succinimide is prepared from polyisobutylenesuccinic anhydride and tetraethylenepentamine.
 5. The fuel additive ofclaim 1 wherein the polyisobutylene of the alkyl-substituted succinimideis prepared from about 850 to 2100 molecular weight polyisobutylene. 6.The fuel additive of claim 1 wherein the polyisobutylene of thealkyl-substituted succinimide is prepared from about 850 to 1300molecular weight polyisobutylene.
 7. The fuel additive of claim 1wherein the polyisobutylene of the alkyl-substituted succinimide isprepared from about 950 molecular weight polyisobutylene.
 8. The fueladditive of claim 1 wherein the composition comprises an organometalliccomplex of manganese, an overbased calcium sulfonate detergent, and anashless alkyl-substituted succinimide dispersant such that when theadditive composition is dissolved in a distillate fuel, the followingrelationship is satisfied:−0.159x+0.243y−0.0143xy≦−8.4 where x=concentration of succinimide (inpounds per thousand barrels) y=concentration of overbased calciumsulfonate (in PTB) with the following limitations: x=20-35, andy=10-120.
 9. The fuel additive of claim I wherein the overbased calciumsulfonate has a TBN of above about
 200. 10. The fuel additive of claim 1wherein the overbased calcium sulfonate has a TBN of about
 300. 11. Afuel comprising a major amount of a middle distillate fuel and a minoramount of a fuel additive composition comprising an organometallicmanganese compound, an alkyl-substituted succinimide ashless dispersant,and an overbased calcium sulfonate detergent of TBN about
 300. 12. Amethod for improving the cleanliness of a fuel intake systems by use inthe fuel intake system of a fuel containing a distillate fuel additivecomposition comprising an organometallic manganese compound, analkyl-substituted succinimide ashless dispersant, and an overbasedcalcium sulfonate detergent of TBN about 300.